Main Navigation

Main Content

A non-profit publication of the Office of the University Relations of Virginia Tech,
including The Conductor, a special section of the Spectrum printed 4 times a year

Barker's book looks at the history of highway bridges

By Lynn Nystrom

Spectrum Volume 20 Issue 06 - October 2, 1997

"Usually, a history of bridges begins with a log across a small stream or
vines suspended above a deep chasm...followed by the development of the stone
arch by the Roman engineers of the second and first centuries B.C. and the
building of the beautiful bridges across Europe during the Renaissance," wrote
Richard M. Barker, Virginia Tech professor of civil engineering, in his new
collaborative book called Design of Highway Bridges.
Barker, along with his co-author Jay Puckett, professor of civil and
architectural engineering at the University of Wyoming, treats the history of
bridges differently--they have elected to highlight bridges that are typical of
those found in the U.S.
The authors' romance with bridge building is apparent. In more than 1,000
pages, they outline the successes and failures of the architects and engineers
who made their fortunes or often met their demise with these structures. These
designers dabbled in various materials such as stone, iron, reinforced
concrete, wood, steel, and various combinations, often without knowing all of
the consequences.
Barker and Puckett's book is complete with historical tidbits. For example,
the oldest remaining Roman stone arch is from the seventh century B.C., and is
a vaulted tunnel near the Tiber River. But the Turks can claim the honor of
having constructed the oldest surviving stone-arch structure, a ninth-century
B.C. historical site over the Meles River in Smyrna.
Compared to these early beginnings, the stone-arch bridges in the U.S. are
"relative newcomers," according to Barker and Puckett. However, the oldest
bridge in the U.S. that continues to serve as part of a highway system is a
stone arch over Pennypack Creek on the King's Road between New York City and
Philadelphia. It was built in 1697.
"A good bridge engineer must never forget the people factor," in their
examination of key bridge types, selection processes, and aesthetic
considerations, wrote the two professors.
The people who built the first bridges in the U.S. were millwrights or
carpenter-mechanics, and did not have a clear understanding of trusses, they
explain. These first bridge engineers used the knowledge they gained from
building large mills and just increased the spans.
Barker and Puckett speak of the railroad as driving the change in bridge
construction in the U.S. When people in America started traveling by rail, the
wooden bridges that had been serving the public well as they moved around in
their horse drawn carriages, were no longer an option. Iron rods replaced wood
tension parts and a hybrid truss composed of a combination of wood and metal
members was made. Eventually, the transition was made to all-metal trusses.
Iron soon became another option.
"Suspension bridges capture the imagination of people everywhere," Barker and
Puckett say. The image of a swinging bridge across a raging torrent of a
rock-strewn river stimulates emotions from fascination to fear to awe.
In their book, Barker and Puckett discuss suspension bridges made of
wrought-iron chains, ones with clear spans of up to 486 meters, and structures
that fell down. With the latter, they note, an early suspension bridge was
aerodynamically unstable, yet the lesson to the engineering profession was lost
for many years. They cite as an example the crash of the Wheeling Suspension
Bridge over the Ohio River some 80 years before the similar demise of the
Tacoma Narrows Suspension Bridge.
The authors note another hazard of the bridge building profession--the
placement of bridge foundations on a solid footing and not on the shifting
sands of a river bed. When James B. Eads designed the steel-deck arch bridge
across the Mississippi River at St. Louis in 1874, he realized that underwater
abutments and piers founded on bedrock would be needed to hold the bridge's
foundations. Wooden boxes, or caissons, were pressurized to keep the water out
and permitted excavation though the river bed to bedrock. Of the workers who
were sent to accomplish this task, 13 men lost their lives due to caisson's
disease, more commonly known as the bends.
The process for constructing with caissons was altered by Eads, who happened
to be a diver, and his physician. They were the ones to suggest a slower
decompression and shorter working time in the caisson as the depth increased.
Consequently, only one additional life was lost. On a brighter note, this
bridge produced a milestone in the field because of its cantilever construction
of the three arches.
Again, Barker and Puckett point out that this advancement in bridge building
was not immediately passed on. The simultaneous construction of the Brooklyn
Bridge by Washington Roebling resulted in his body being stricken by the bends,
and his partial paralysis for life.
Barker and Puckett's history continues, citing progress in reinforced-concrete
bridges, the first of which remains in service in Golden Gate Park, San
Francisco, and the development of girder bridges, the most numerous of all
highway bridges in the U.S.
"The challenge for today's bridge engineer is to follow in the footsteps of
these early designers and create and build bridges that other engineers will
write about 100 and 200 years from now," they wrote.
The remainder of their book focuses on aesthetics, an in-depth examination of
design considerations, separate chapters on concrete, steel, and timber
structures, system analysis procedures, sample problems, and selected
references for further study. Their book is the first treatise on highway
bridges to be based on load-and-resistance-factor design principles recently
developed by the American Association of State Highway and Transportation
Officials. Design of Highway Bridges is published by John Wiley &
Sons, Inc.